Rotary percussion gang drill



June 11, 1968 R. 1.. THOMPSON ROTARY PERCUSSION GANG DRILL Filed March 15. 1966 INVENTOR. ROBERTL. THOMPSON United States Patent "ice 3,387,673 ROTARY PERCUSSION GANG DRILL Robert L. Thompson, Easton, Pa, assignor to lngersoil- Rand Company, New York, N.Y., a corporation of New Jersey Filed Mar. 15, 1966, Ser. No.

8 Claims. (Cl. 175-96 ABSTRACT OF THE DISCLOSURE A gang drill for drilling la nge holes which includes a plurality of down-the-hole drills mounted on a body. A central down-the-hole drill having a percussive button bit mounted thereon drills a pilot hole. The remainder of the drills are provided with either a roller bit or a percussive bit. Each bit is hammered independently by its associated down-the-hole drill. The roller bits carry most of the weight of apparatus while the percussive button bits do most of the drilling.

This invention relates to gang drills and more particularly to an improvement over U.S. Patent No. 3,144,- 086, issued to E. H. Kurt and J. W. Adams.

Said U.S. Patent No. 3,144,086 discloses apparatus having a body supporting a plurality of down-the-hole drills. The rear of the body has a central passage supplying air to the down-the-hole drills. Each down-thehole drill is provided with a conventional percussion bit having tungsten carbide inserts. A 'down-the-hole drill is a drill having a fluid powered hammer or percussive means which travels down the hole with the bit. An example of a down-the-hole drill is shown in U.S. Patent No. 3,198,264, issued to E. S. Oelke et al.

In prior gang drills employing a plurality of conventional drill bits such as that shown in U.S. Patent No. 3,144,086, accurate weight control is essential to prevent breakage of the bits and particularly the carbide inserts. By weight control is meant the amount of weight of the assembly which is supported by the drill bit. The tungsten carbide inserts wear and often break because when the insert is embedded in the rock and then rotated, great forces are exerted on these inserts.

In gang drills employing exclusively roller cones, a great deal of thrust and torque must be delivered to the roller cone bits for the drill to be workable.

It is therefore the principal object of this invention to provide a gang drill in which the life of the bits is prolonged.

It is another object of this invention to provide a device for boring large holes which eliminates the problem of weight control.

In general, the above objects are carried out by providing a gang drill comprising: a body; a plurality of fluid pressure operated down-the-hole drills mounted on said body in parallel relationship to each other; one of said drills being mounted on the longitudinal axis of said body and having a center bit operatively connected thereto and the remainder of said drills being circumferentially spaced around the drill mounted on the longitudinal axis; a drill bit operatively connected to each of the circumferential drills and adapted to be hammered by its associated drill; at least one of the drill bits being a roller bit; and at least one of the drill bits connected to the circumferential drills being a percussion bit.

These and other objects will become apparent from the following description and accompanying drawings in which:

FIG. 1 is a perspective view of a gang drill embodying this invention;

3,387,673 Patented June 11, 1968 FIG. 2 is a bottom plan view of the invention; and

FIG. 3 is a section taken on the lines 3-3 of FIG. 2 in the direction of the arrows with the section being opened up and the outer bits shown in elevation for purposes of clarity.

Referring to the drawings in detail, the gang drill Comprises a body generally indicated at 1. A plurality of down-the-hole drills are mounted on the body. These drills include a center drill 2 and four outer drills 3-, 4 which are circumferentially spaced around the center drill 2. The center drill 2 is mounted on the longitudinal axis of the body 1 and projects forward of the circumferential drills 3 and 4, and thus acts as a pilot bit.

There are screw threads (not shown) around a portion of the casing of the center down-the-hole drill 2 so that this drill can be screwed into the chuck 24 on the body 1 and be held in place. Each of the circumferential down-the-hole drills 3-, 4 are held against rotation on the body 1 by a chuck 5 having grooves 6 which engage pins 7. The upper portion of the back head 8 of the drills is threaded. The back head 8 is slidably received in a hollow holder 9 and a cap nut 10 is screwed onto the back head.

There is a generally circular button bit 11 slidably mounted in the forward end of the center down-the-hole drill 2. A button bit is known by those in the art to be a percussion bit of any desired shape having a plurality of tungsten carbide or other hard mate-rial buttons which project out of that portion of the body of the bit which contacts the rock face. These buttons are indicated at 12 on bit 11.

A wedge-shaped button bit 13 is slidably mounted on each of two of the drills 3. The button bits 13 should be arranged so that they are oppositely disposed as best shown in FIG. 2. The buttons 14 on the bit 13 should be distributed proportional to the shape of the bit, i.e. there should be more buttons at the outer edge of the bit than at the inner edge. The distribution of the buttons 14 in this manner promotes even wear and faster drilling.

Each of the bits 11 and 13 has an integral splined portion 15 above the cutting portion. This splined portion fits into the open end of the drill and is arranged so that the bit will move downward or forward relative to the drill when it is hammered.

There are two oppositely disposed roller cone bits 16. Each roller bit 16 is rotatably mounted on a shank 17 and adapted to roll when the body is rotated. The shank 17 is mounted in drill 4 by a splined portion 18. The splined portion allows the shank and thus the roller bit 16 to move downward relative to the drill when the shank is hammered. Each roller cone is provided with a plurality of tungsten carbide inserts or buttons 19.

The shanks 17 should be of such a length that the roller cones 16 project slightly forward of the button bits 13 as best shown in FIG. 3. By projecting slightly forward, the roller cones contact the surface to be bored before the button bits 13 and thus carry most of the weight of the assembly.

In operation, the gang drill is attached to a hollow to bits to drill a large hole, the roller cones carry most of the weight while the button bits do most of the drilling but ca'nry little or no weight. By using this arrangement, accurate weight control is not essential. Button bits do not wear as fast as conventional percussion bits and therefore the drilling operation can be carried on longer without changing bits. The outer edges of the conventional bit wear faster. This necessitates that each bit be periodically rotated in the drill with respect to the other bits. Roller cones when used exclusively require a lot of thrust and torque.

Although an assembly has been shown which employs only a pair of oppositely disposed button bits and a pair of oppositely disposed roller cones, if desired, the number of button bit sand roller cones may be increased, as long as button bits are opposite each other and roller cones are opposite each other. Only one type of holding means has been shown, but, if desired, the down-thehole drills may be held on the body in other ways.

Although a preferred embodiment has been shown and described, it is intended that the invention not be limited in any Way except by the appended claims.

I claim:

1. A gang drill comprising:

a body;

a plurality of fluid pressure operated down-the-hole drills mounted on said body in parallel relationship to each other;

one of said drills being mounted on the longitudinal axis of said body and having a center bit operatively connected thereto and the remainder of said drills being circumferentially spaced around the drill mounted on the longitudinal axis;

a drill bit operatively connected to each of said drills and adapted to be hammered by its associated drill;

at least one of the drill bits connected to the circumferential drills being a roller bit; and

at least one of the drill bits connected to the circumferential drills being a percussion bit.

2. A gang drill according to claim 1 wherein there are at least a pair of roller bits oppositely disposed to each other, and at least a pair of percussion bits 0ppositely disposed to each other.

3. The gang drill of claim 2 wherein said percussion bits are button bits of generally wedge shape having the buttons distributed proportional to the shape of the bit.

The gang drill of claim 1 wherein said down-thehole drills are supplied with fluid through said body.

5. The gang drill of claim 1 wherein said center bit projects forward of said roller and percussion bits to act as a pilot bit.

6. The gang drill of claim 5 wherein said center bit is a button bit.

7. The gang drill of claim 6 wherein said center bit is generally circular in shape.

8. The gang drill of claim 1 wherein said center bit projects forward of said roller and percussion bits, and said roller bits project slightly forward of said percussion bits.

References Cited UNITED STATES PATENTS 1,062,050 5/1913 Stewart -96 2,466,709 4/1949 Kanr 17596 X 2,942,850 6/1960 Heath 176-96 3,144,086 8/1964 Kurt 17596 3,297,099 1/1967 Adams 17596 NILE C. BYERS, ]R., Primary Examiner. 

